CN113185873B - A kind of preparation method of bio-based flame retardant and anti-photoaging PVA composite material - Google Patents

Abstract

The invention discloses a preparation method of a bio-based flame-retardant and anti-photoaging PVA composite material, which comprises the steps of dispersing polyvinyl alcohol in deionized water, heating, stirring and cooling to obtain PVA dispersion liquid; adding glacial acetic acid and chitosan powder, and stirring at room temperature until the chitosan powder is completely dissolved; adding phytic acid, stirring and performing ultrasonic treatment to obtain a bio-based flame-retardant PVA solution; adding fluorescent powder, stirring at room temperature, and performing ultrasonic treatment to obtain a mixed solution; and transferring the mixed solution into a mold for drying and demolding to obtain the bio-based flame-retardant and anti-photoaging PVA composite material. The composite material prepared by the preparation method has excellent flame retardant property, mechanical property, ultraviolet absorption property and the like, can reduce the influence of ultraviolet on PVA, and can improve the service life and the light aging resistance.

Description

A kind of preparation method of bio-based flame retardant and anti-photoaging PVA composite material

technical field

The invention belongs to the technical field of composite materials, relates to a flame-retardant composite material, and in particular relates to a preparation method of a bio-based flame-retardant and anti-photoaging PVA composite material.

Background technique

Resin-based composite materials such as polyvinyl alcohol (PVA) have the characteristics of high specific strength, low density, fatigue resistance, shock absorption, chemical corrosion resistance, etc., and are widely used in various industries and people's daily life. However, its flammability also leads to the potential hidden danger of fire, which threatens people's life safety all the time. For this reason, flame retardants are usually added to reduce the flammability of PVA and improve its safety. However, adding a large amount of flame retardants will have a great impact on the mechanical properties of the material and its inherent excellent properties. On the other hand, PVA will be affected by various environmental factors when used outdoors, and it is especially susceptible to photo-oxidation by ultraviolet light, resulting in loss of luster, discoloration, cracking and embrittlement of PVA, which reduces its performance. Adding UV absorbers can inhibit the photoaging of PVA, prolong the service life, save resources, reduce costs, and reduce environmental pollution. Common UV absorbers, such as TiO ₂ , ZnS, etc., will generate strong oxidizing holes and strong reducing photo-generated electrons after absorbing ultraviolet light. These holes and electrons will react with oxygen, water and other substances to generate chemical activity. Higher levels of free radicals will react with PVA, reducing the properties of the polymer material and eventually leading to its decomposition.

Bio-based flame retardants have the advantages of environmental protection, no pollution, high efficiency and wide source of raw materials. Among them, PA and CH are the most commonly used flame retardants in bio-based flame retardants, and their surface charges are different, making them possible to combine. Therefore, through the reaction of PA and CH at a specific pH value, a green and environmentally friendly bio-based polyelectrolyte composite was synthesized, and it was composited with PVA. The prepared flame retardant composite material not only has excellent flame retardant properties , while improving its mechanical properties. On this basis, adding fluorescent powder with UV-absorbing function to the above system can inhibit the photoaging of PVA and prolong its service life, thus providing the possibility for the preparation of multifunctional flame retardant composite materials.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of a bio-based flame retardant and anti-photoaging PVA composite material, which can produce a PVA composite material with excellent flame retardant properties, excellent mechanical properties and strong anti-photoaging properties.

In order to achieve the above object, the technical scheme adopted in the present invention is: a preparation method of a bio-based flame retardant and anti-photoaging PVA composite material, which is specifically carried out according to the following steps:

Step 1: Disperse 2-5 g of polyvinyl alcohol (PVA) in 100-250 mL of deionized water, heat up to 80-95 ° C, stir for 1-3 h, and naturally cool to room temperature to obtain a PVA dispersion;

The degree of polymerization of polyvinyl alcohol was 1750.

Step 2: Add 0.5-2 mL of glacial acetic acid and 0.1-1 g of chitosan powder to 100-250 mL of PVA dispersion, and stir at room temperature for 2-4 hours until the chitosan powder is completely dissolved to obtain a mixed solution; add 0.25-8 g of chitosan powder; Phytic acid is added to the mixture, stirred at room temperature for 1 to 2 hours, and then ultrasonicated for 1 to 4 hours to obtain a bio-based flame retardant PVA solution;

Bio-based flame retardants are polyelectrolyte composite flame retardants that can be obtained by reacting phytic acid (PA) and chitosan (CH) in the pH range of 1 to 5. The resulting particles are smaller, and the pH is set at about 2 in the preparation method of the present invention.

Step 3: Add fluorescent powder to the bio-based flame-retardant PVA solution obtained in step 2, and the mass of the added fluorescent powder is 3-5% of the total mass of the bio-based flame-retardant PVA solution and the added fluorescent powder, and stir at room temperature for 4 ~6h, then ultrasonic for 1~2h to obtain a mixed solution;

The fluorescent powder used is a fluorescent powder that has excitation in the wavelength band of 200nm-400nm.

The preferred phosphors are prepared as follows:

A. According to the stoichiometric ratio of each chemical composition in the chemical expression Sr _1.7 Ba _0.3 Si _4.7 Al _0.3 N _7.7 O _0.3 : 0.05Eu ²⁺ , take Sr ₃ N ₂ , Ba ₃ N ₂ , Si ₃ N ₄ , AlN respectively , Al ₂ O ₃ and EuF ₃ , and then weigh the flux (Li ₃ N) and the impurity removal agent (carbon powder) with a mass fraction of 1 wt% respectively, grind the obtained raw materials into powder, and mix them uniformly to obtain raw powder;

B. The raw material powder is placed in a closed environment with a protective atmosphere, heated to 1500°C at a heating rate of 5°C/min, calcined for 4 hours, and cooled to room temperature to obtain a calcined product;

C. Grinding the calcined product to obtain Sr _1.7 Ba _0.3 Si _4.7 Al _0.3 N _7.7 O _0.3 :0.05Eu ²⁺ phosphor.

Step 4: Transfer the mixed solution to a mold, dry it in a drying oven at 60° C. for 6 hours, and release the mold to obtain a bio-based flame-retardant and photoaging-resistant PVA composite material.

The composite material prepared by the preparation method of the invention is composed of a resin matrix, a flame retardant additive and a fluorescent powder. The flame retardant additives are chitosan and phytic acid. The resin is polyvinyl alcohol resin. The mass of flame retardant additives accounts for 5-20% of the total mass of the composite material. Phosphors account for 3 to 5% of the total mass of the composite material.

Bio-based polyelectrolyte composite flame retardant can significantly improve the mechanical properties of PVA composites. The reasons can be attributed to the following three points: First, CH is contained in the composite material. Compared with PVA, CH has a larger molecular weight, and the carbon skeleton is more stable and harder. Secondly, the interaction between pure PVA molecules is mainly through hydrogen bonds, which is a weak interaction force, while the bio-based polyelectrolyte composite flame retardant and PVA will form phosphonate bonds under the action of ultrasound (strong interaction force) to replace part of the hydrogen bonds, which is beneficial to improve the mechanical properties. Finally, the polyelectrolyte complex formed by the reaction of phytic acid and chitosan is dispersed into the PVA molecular chain, which hinders the movement of the PVA molecular chain, so that the movement of the PVA molecular chain is hindered, so a larger force is required during the stretching process. The PVA molecular chain moves and breaks. Therefore, the multifunctional flame-retardant PVA composite material prepared by the present invention has excellent mechanical properties.

Phosphorus-containing compounds produced during the decomposition of bio-based polyelectrolyte composite flame retardants can catalyze the dehydration of the matrix into carbon, which is beneficial to hinder heat transfer and volatilization of combustibles. In the gas phase, phosphorus-containing compounds will generate phosphorus-containing groups (PO•, HPO•) during the combustion reaction. These phosphorus-containing groups can effectively capture the free radicals generated during the combustion process, thereby cutting off the combustion reaction. In addition, during the combustion process of nitrogen-containing compounds, refractory gases (such as ammonia, nitrogen and water vapor, etc.) will be released, thereby diluting combustible gases and oxygen and taking away heat. Therefore, the bio-based flame-retardant PVA composite material prepared by the preparation method of the present invention has excellent flame-retardant properties.

TiO ₂ , ZnS, etc. will generate strong oxidizing holes and strong reducing photo-generated electrons after absorbing ultraviolet rays. These holes and electrons will react with oxygen, water and other substances, and those with higher chemical activity will occur with PVA. The reactive free radicals reduce the properties of the polymer material and eventually lead to its decomposition. The holes and electrons generated by the phosphor added in the preparation method of the present invention after absorbing ultraviolet rays will be recombined and consumed within nanoseconds to microseconds, and will not participate in the reaction with oxygen and water.

The preparation method of the present invention has the following advantages:

1) In the prepared composite material, a bio-based polyelectrolyte composite flame retardant is added, which has the advantages of less additive amount, wide source of raw materials and low cost.

2) Bio-based polyelectrolyte composite flame retardants belong to bio-based flame retardants. They are halogen-free, environmentally friendly, non-toxic and non-corrosive. They do not produce toxic waste during preparation and use, and are environmentally friendly. flame retardant.

3) In addition to excellent flame retardant properties, the obtained PVA composite material is also due to the addition of phosphors, which benefit from the effect of phosphors absorbing ultraviolet rays, which reduces the influence of PVA by ultraviolet rays, and improves its life and light resistance. Aging properties.

4) The matrix of the prepared composite material is PVA, so it has a wide range of applications and can be used in architectural coatings and other coatings fields.

5) The prepared composite material has excellent flame retardant properties, mechanical properties and UV absorption properties.

Description of drawings

Figure 1 is a graph of the UL-94 test results of the PVA composite material prepared in Example 3, wherein the picture a is the appearance picture before the test, and the picture b is the appearance picture after the test.

Figure 2 is a graph of the LOI test results of the PVA composite material prepared in Example 3, wherein the picture a is the appearance picture before the test, and the picture b is the appearance picture after the test.

Fig. 3 is the XRD pattern of the phosphor in the preparation method of the present invention.

FIG. 4 is the DRS diagram of the PVA composite material prepared in Example 3 and the polyvinyl alcohol sample prepared in the comparative example.

FIG. 5 is an excitation spectrum diagram of the phosphor in the preparation method of the present invention.

6 is a bar graph of the tensile strength of the PVA composite materials prepared in Examples 1 to 3 and the polyvinyl alcohol samples prepared in the comparative example.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Example 1

Disperse 2 g of polyvinyl alcohol with a degree of polymerization of 1750 in 100 mL of deionized water, heat up to 80 °C, stir for 1 h, and naturally cool to room temperature to obtain a PVA dispersion; add 0.5 mL of glacial acetic acid and 0.1 g of glacial acetic acid to 100 mL of the PVA dispersion. Chitosan powder was stirred at room temperature for 2 hours until the chitosan powder was completely dissolved to obtain a mixed solution; 0.25 g of phytic acid was added to the mixed solution, stirred at room temperature for 1 hour, and then sonicated for 1 hour to obtain a bio-based flame retardant PVA solution ; To the bio-based flame retardant PVA solution, add a phosphor that has excitation in the 200nm-400nm band, and the mass of the added phosphor is 3% of the bio-based flame retardant PVA solution and phosphor, stir at room temperature for 4h, and then ultrasonicate for 1h , to obtain a mixed solution; transfer the mixed solution to a mold, dry it in a drying oven at 60° C. for 6 hours, and release the mold to obtain a bio-based flame retardant and anti-photoaging PVA composite material.

Example 2

Disperse 5g of polyvinyl alcohol with a degree of polymerization of 1750 in 250mL of deionized water, heat up to 95°C, stir for 3h, and naturally cool to room temperature to obtain a PVA dispersion; add 2mL of glacial acetic acid and 1g of chitosan to 250mL of the PVA dispersion sugar powder, stirred at room temperature for 4 hours, until the chitosan powder was completely dissolved to obtain a mixed solution; 8 g of phytic acid was added to the mixed solution, stirred at room temperature for 2 hours, and then sonicated for 4 hours to obtain a bio-based flame retardant PVA solution; The bio-based flame-retardant PVA solution is added with phosphors that have excitation in the 200nm-400nm band, and the mass of the added phosphor is 5% of the total mass of the bio-based flame-retardant PVA solution and the phosphor powder, stirred at room temperature for 6 hours, and then ultrasonicated for 2 hours. A mixed solution was obtained; the mixed solution was transferred to a mold, dried in a drying oven at 60° C. for 6 hours, and demolded to obtain a bio-based flame-retardant and photoaging-resistant PVA composite material.

Example 3

Disperse 3.5 g of polyvinyl alcohol with a degree of polymerization of 1750 in 175 mL of deionized water, heat up to 87.5 °C, stir for 2 h, and naturally cool to room temperature to obtain a PVA dispersion; add 1.25 mL of glacial acetic acid and 0.55 mL of glacial acetic acid to 175 mL of the PVA dispersion. g chitosan powder, stirred at room temperature for 3 hours, until the chitosan powder was completely dissolved, to obtain a mixed solution; 4.125 g of phytic acid was added to the mixed solution, stirred at room temperature for 1.5 hours, and then sonicated for 2.5 hours to obtain a biological resistance Burn the PVA solution; add phosphors excited in the 200nm-400nm band to the bio-based flame-retardant PVA solution, the mass of the added phosphors is 4% of the total mass of the bio-based flame-retardant PVA and phosphors, and stir at room temperature for 5h , and then ultrasonicated for 1.5 h to obtain a mixed solution; the mixed solution was transferred to a mold, dried in a drying oven at 60° C. for 6 h, and demolded to obtain a bio-based flame retardant and anti-photoaging PVA composite material.

Comparative ratio

Disperse 5 g of polyvinyl alcohol (PVA) with a degree of polymerization of 1750 in 250 mL of deionized water, heat up to 95 °C, stir for 3 hours, and naturally cool to room temperature to obtain a PVA dispersion; dry in a 60 °C drying box for 6 hours to obtain polyethylene Alcohol samples.

The bio-based flame retardant and anti-photoaging PVA composite materials prepared in Examples 1-3 and the polyvinyl alcohol samples prepared in the comparative example were subjected to limiting oxygen index test and vertical combustion test, and the results are shown in Table 1.

Table 1 Vertical combustion and limiting oxygen index test results of composite materials prepared in Examples 1-3 and polyvinyl alcohol samples prepared in Comparative Example

It can be seen from Table 1 that the limiting oxygen index of the PVA composite materials prepared in Examples 1 to 3 is significantly improved with the increase of the amount of flame retardant added, which proves that compared with pure polyvinyl alcohol, the preparation method of the present invention has The flame retardant properties of the PVA composites were significantly improved. In Example 2, when the addition amount of the flame retardant reaches 10%, its limiting oxygen index can reach 30%, and only 10% addition amount can make the oxygen index of the composite material reach a higher value. When the addition amount reaches 20%, the vertical combustion level reaches V-0 level. It is proved that the bio-based flame retardant prepared by the preparation method of the present invention has excellent flame retardant efficiency.

The UL-94 test result diagram of the PVA composite material prepared in Example 3 is shown in Figure 1, wherein the picture a is the appearance picture before the test, and the picture b is the appearance picture after the test. The LOI test result diagram of the PVA composite material prepared in Example 3 is shown in Figure 2. Figure a in Figure 2 is the appearance picture before the test, and Figure b in Figure 2 is the appearance picture after the test. It can be seen from Figure 1 and Figure 2 that the sample basically maintains its original shape after combustion, and the combustion self-extinguishes without dripping. This is mainly due to the flame retardant effect of the flame retardant in the gas phase and the condensed phase. The phosphorus-containing compounds produced by the bio-based polyelectrolyte composite flame retardant during the decomposition process can catalyze the dehydration of the matrix into carbon, which is beneficial to hinder heat transfer and facilitate the volatilization of fuel. In the gas phase, phosphorus-containing compounds will generate phosphorus free radicals (PO••, HPO•) during the combustion reaction. These free radicals can capture the free radicals of the combustion cycle in the gas phase, and also release fire-resistant gas to dilute the combustible gas, oxygen and heat. Thus, the composite material has excellent flame retardant properties.

Figure 3 is the XRD pattern of the phosphor used in the example, it can be seen that the XRD of the sample is consistent with the PDF card, which proves that it has no impurities. Figure 4 is the DRS diagram of the PVA composite material prepared in Example 3 and the polyvinyl alcohol sample prepared in the comparative example. It can be observed that in the 200-400 nm wavelength band, the composite film transmits less light compared to the pure PVA sample. It shows that the composite flame retardant material with added phosphor absorbs most of the ultraviolet light in this band, reduces the influence of ultraviolet light on the life of polyvinyl alcohol, and achieves the performance of anti-photoaging. Figure 5 is the excitation spectrum of the phosphor used in the example. It can be seen that the phosphor exhibits a broadband excitation of 250-550 nm under the monitoring of 606 nm, which shows that the phosphor can effectively absorb the near-ultraviolet wavelength of 250-550 nm, which is the same as that shown in Fig. 4 UV absorption results are consistent.

The test results of the mechanical properties of the PVA composite materials prepared in Examples 1 to 3 and the polyvinyl alcohol samples prepared in the comparative example are shown in Figure 6. It can be seen that the tensile strength of the prepared PVA composite materials has been significantly improved. This is due to Compared with pure PVA, CH is contained in the PVA composite material, the molecular weight of CH is large, and the carbon skeleton is more stable and hard. Secondly, the interaction between pure PVA molecules is mainly through hydrogen bonds, which is a weak interaction force, while the bio-based polyelectrolyte composite flame retardant and PVA will form phosphonate bonds under the action of ultrasound (strong interaction force) to replace part of the hydrogen bonds, which is beneficial to improve the mechanical properties. Finally, the polyelectrolyte complex formed by the reaction of phytic acid and chitosan was dispersed into the PVA molecular chain, hindering the movement of the PVA molecular chain. Therefore, the multifunctional flame-retardant PVA composites prepared have excellent mechanical properties.

Claims (3)

1. A preparation method of a bio-based flame-retardant and anti-photoaging PVA composite material is characterized by comprising the following steps:

step 1: dispersing 2-5 g of polyvinyl alcohol in 100-250 mL of deionized water, heating to 80-95 ℃, stirring for 1-3 h, and naturally cooling to room temperature to obtain a PVA dispersion liquid;

step 2: adding 0.5-2 mL of glacial acetic acid and 0.1-1 g of chitosan powder into 100-250 mL of PVA dispersion liquid, and stirring at room temperature until the chitosan powder is completely dissolved; adding 0.25-8 g of phytic acid, stirring at room temperature for 1-2 h, and performing ultrasonic treatment for 1-4 h to obtain a bio-based flame-retardant PVA solution;

and step 3: adding fluorescent powder into the bio-based flame-retardant PVA solution, wherein the mass of the added fluorescent powder is 3-5% of the total mass of the bio-based flame-retardant PVA solution and the added fluorescent powder, stirring for 4-6 h at room temperature, and performing ultrasonic treatment for 1-2 h to obtain a mixed solution;

the fluorescent powder is prepared by the following steps:

A. according to chemical expression Sr_1.7Ba_0.3Si_4.7Al_0.3N_7.7O_0.3:0.05Eu²⁺The stoichiometric ratio of the chemical compositions is Sr₃N₂、Ba₃N₂、Si₃N₄、AlN、Al₂O₃And EuF₃Respectively weighing 1wt% of fluxing agent and impurity removing reagent, grinding the taken raw materials into powder, and uniformly mixing to obtain raw material powder;

B. placing the raw material powder in a closed environment with protective atmosphere, heating to 1500 ℃ at the heating rate of 5 ℃/min, roasting for 4h, and cooling to room temperature to obtain a calcined substance;

C. grinding the calcined product to obtain Sr_1.7Ba_0.3Si_4.7Al_0.3N_7.7O_0.3:0.05Eu²⁺Fluorescent powder;

and 4, step 4: and transferring the mixed solution into a mold, drying for 6 hours at the temperature of 60 ℃, and demolding to obtain the bio-based flame-retardant and anti-photoaging PVA composite material.

2. The preparation method of the bio-based flame-retardant and anti-photoaging PVA composite material according to claim 1, wherein in the step 1, the polymerization degree of the polyvinyl alcohol is 1750.

3. The method for preparing a bio-based flame-retardant and anti-photoaging PVA composite material according to claim 1, wherein in the step 3, the phosphor is a phosphor excited at a wavelength band of 200nm to 400 nm.

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